1. Field of the Invention
This invention relates to the field of antigen-antibody reaction measurement using a carrier such as latex which is utilized in the field of immunology.
2. Related Background Art
Heretofore, as an immunity inspecting method, use has been made of a method in which a suspension comprising a mixture of a carrier such as latex sensitized by a predetermined antibody and a specimen sample is prepared and where an antigen to be specified is contained in the specimen sample, an antigen-antibody reaction occurs between the antigen and the sensitized antibody and carrier particles are coupled together and the presence of the antigen in the specimen sample or the amount of the antigen is measured from the condensed state of the carrier. In that case, a method of discriminating the condensed state of the carrier has been carried out by measuring the absorbance of the suspension including the carrier or the degree of light scattering of the suspension. Particularly, by the use of flow cytometry, that is, by wrapping the suspension in sheath liquid, hydrodynamically converging it, causing individual carriers to flow to an inspecting position in succession, applying a light beam to the carrier at the inspecting position and judging the size of the carrier from the intensity of scattered light, it has been possible to judge the condensed state of the individual carriers and calculate the presence of the antigen or the amount of the antigen and accomplish highly accurate measurement. A specific example of it is described, for example, in U.S. Pat. No. 4,521,521. However, in the above-described example of the prior art, only a carrier sensitized by one kind of antibody can be used and only the inspection of one kind of antigen can be effected at a time, and this has formed a hindrance in enhancing the efficiency during mass medical examination.
As an example of the method of solving this problem, a method in which a plurality of kinds of fine particles differing in the kind of fluorescence or the particle diameter are used to measure a plurality of kinds of antigen-antibody reactions at a time is described in Japanese Laid-Open Patent Application No. 62-81567. According to this method, discrimination between the kinds of the fine particles is done by the fluorescence wavelength or a combination of the fluorescence wavelength and the particle diameter. If the particle diameter is only made to differ for a plurality of kinds of particles, the kinds of the particles cannot be distinguished in the case of a condensed state of the same size and therefore, it is necessary to distinguish between them by the fluorescence. However, the intensity of the fluorescence which occurs is weak and therefore, it has been difficult to reliably discriminate between the kinds of the particles from the fluorescence. Further, with an optical system for detecting scattered light, a precise optical system for detecting the weak fluorescence has been separately necessary.